I don't know where the historic gold/silver ratio of 15:1 comes...

I don't know where the historic gold/silver ratio of 15:1 comes from. I have been tracking the ratio for some 35 years now and can say that the historic ratio is nearer to 40:1. Once in 1980 it hit 15:1 but that was about the time that the Hunt brothers were trying to corner the silver market.

Just to confirm that, Google gold/silver price ratio. The figures aren't mine, they are historical numbers.